Circuit interrupter



April 13, 1937. H. J. LING'AL ET AL CIRCUIT INTERRUPTER Filed Sept. 12,1934 2 Sheets-Sheet 1 INYENT Harry-f llflga/ and WITNESSES A'TTORNE H.J.LINGAL ET AL CIRCUIT INTERRUPTER April 13, 1937.

2 Sheets- Sheet 2 Filed Sept. 12, 1934 WITNESSES: d7ff%z.

Patented Apr. 13, 1937 UNITED STATES PATENT OFFICE cIncUrr mmaamaaApplication September 12, 1934, Serial No. 743,696 20 Claims. (01.200-150) Our invention relates generally to circuit interrupters and hasparticular application to contact structures for high-capacity electricswitches.

In recent years, it has become increasingly common practice in theelectrical art to interconnect alternating current power distributionsystems into large networks which may extend over large areas, and whichmay include a great number of separate sources of power. These systemsordinarily transmit alternating current power at high voltages, whichfact in combination with the large amounts of available power, causesthe problem of circuit interruption of fault currents to be oneof'particular seriousness.

To insure system stability, even very large overloads must beinterrupted within extremely short periods of time, often less than onecycle. This necessitates extremely rapid movement of the separatingcontact members in order that 9 an arc of considerable length may bedrawn during the allowable period of circuit interruption. At the sametime, the amount of power whichmay be transmitted over the circuit isoften comparatively large, thereby necessitating the use of contactmembers having a very considerable cross-sectional area. In other words,while the contact members must be moved rapidly to prevent undesirablecircuit disturbances, those members must be quite large physio cally,due to the considerable amounts of power normally carried therethrough.The problem is further aggravated, because of the fact that theincreasingly high voltages in use on network systems necessitates acomparatively large amount of contact separation to prevent the are fromrestriking during the circuit interrupting operation.

'The principal object of our invention, therefore, is to provide animproved, high capacity circuit interrupter for use with high-voltagecircuits, our improved device toinclude means for effecting a very rapidseparation of the cooperating contact members within an extremely shortperiod of time. This principal-object of our invention is accomplishedthrough the provision of a contact structure which includes two pairs ofseparable contact members, oneof which is separable prior to-the otherduring the circuit interrupting operation, and means whereby the heatedare products resulting from the separation of the first pair ofseparable contact memhers is caused to effect a more rapid separation ofthe second pair of separable contact members than could be effected bythe actuating mechanism alone. In the preferred embodiment of thisarrangement, one of the pairs of separable contact members opens withina pressure chamber which is filled with a gas evolving substance, andthe pressure of the resulting gas is caused to actuate a movable pistonwhich. effects the separation of the second pair of separable contactmembers.

A further object of our invention is to provide a simple contactstructure wherein the energy of a short are may be utilized foreifecting the separation of a pair of contact members which are disposedwithin an arc extinguishing device.

These and other objects of our invention will be made more apparent byreference to the accompanying drawings wherein are shown twomodifications oi the structure of our invention:

Figure 1 is a sectional view, partially in elevation, showing a circuitinterrupter utilizing contact structures according to our invention;

Fig. 2 is a sectional view through one of the contact structures and oneof the are extinguishing devices embodied in the circuit interruptershown in Fig. 1;

Fig. 3 is an enlarged sectional view on the line IIIHI of Fig. 2;

Fig. 4 is a sectional view on the line IV--IV of Fig. 2;

Fig. 5 is a sectional view through a modified form of contact structurewhich may be used with the device shown in Figure l;

Fig. 6 is a sectional view on the line VL-VI of Fig. 5; and

Fig. 7 is a sectional line on the line VII- VH of Fig. 2.

The circuit interrupter illustrated in Fig. 1 is of the conventional,double-break, fluid immersed type. 'It includes a tank I having thecover 3 bolted thereto, a pairof insulating bushings 5 mounted on thecover through suitable flanges 1 and bolts 9, a pair ofstationarycontact structures ll, one of which is affixed to the lower end of theconductor 13 disposed within each of the insulat- =-ing bushingsi. anarc extinguishing device l5 associated'. with each of the contactstructures H,

albridging member ll adapted to electrically conblage II, and thencethrough the conductor 3 disposed within the right-hand bushing 5.

The contact structures II and the arc extinguishers 5 are normallysubmerged in a body of insulating fluid 2|] which is contained withinthe tank I. This fluid- 20 is preferably one which is capable ofevolving considerable amounts of arc extinguishing gas when placed inproximity to an electric are, both to facilitate the are drawingoperation of the contact structures and the extinguishing operation ofthe arc extinguishers. Oil is a satisfactory fluid.

The preferred embodiment of the stationary contact structures of ourinvention is illustrated in Fig. 2, and each of these includes a supportmember 2| adapted to be bolted to the end of the conductor l3 disposedwithin the cooperating bushing 5, a casing 22, which defines the outerwalls of a pressure chamber, aiflxed to the support member 2| throughthe agency of a flange 23 and a threaded tubular member 25, and a pairof movable contact members 21 and 29, one of which (21) is positionedwithin the tubular member 25 and the other of which (29) ispositionedwithin the pressure chamber 22. The lower end of the castingwhich defines the pressure chamber 22 terminates in a flange 3| which isadapted to serve as a support for the cooperating arc extinguishingdevice l5.

The upper contact member 21 is supported for slidable movement by meansof a guide member 33 positioned within the tubular member 25 and isbiased in the direction of the arc extinguishing device l5 by means of aspring 35. The upper end 31 of the contact member 21 is enlarged, andthis enlarged portion is adapted toengage a suitable cooperating portion39 formed within the guide member 33, the portions 31 and 39 being sorelated that they form a dashpot. which regulates the downward movementof the contact member 21 under the action of the biasing spring 35. Aflexible shunt 4| serves to electrically connect the upper contactmember 21 with the contact support 2|.

The pressure chamber, as is shown particularly in Figs. 2 and 4,comprises a pair of cast, hollow cylinders 22 and 42, one of which (42)is disposed within the other. The space 43 between the outer and theinner cylindrical members comprises the pressure chamber proper and itis within this space that the cooperating contact surfaces of the'uppercontact member 21 and the lower contact member 29 are adapted toseparate.

The space 44 within the inner cylindrical member comprises a pistonchamber whichdirectly connects with the pressure chamber 43. Aninsulating plate 45,,suitable insulating bushings 41, and insulatingwashers 49 serve to electrically insulate the pressure chamber structureand the lower contact member 29 from the flange 23 and the upper contactmember 21. A small vent opening 5| is formed within the flange 23 inorder that the pressure chamber 43 may connect with the main body ofliquid contained within the breaker enclosure.

The lower contact member 29 is provided with a circular support plate 53rigidly aflixed thereto at. its mid-portion and is adapted to beslidably supported through the agency of a suitable guide opening 55formed in the member 51 which encloses the top of the piston chamber 44and a similar guide opening 59 in the bottom of the main closure 22 ofthe pressure chamber. A spring 6|, within the piston chamber 44, engagesthe support plate 53 and biases the second contact member 29 in thedirection of the arc extinguishing device l5. A piston member 63 isnormally positioned within the lower portion of the piston chamber, andwhen moving therein is free to slide for a short distance on the lowercontact member 29. A vent opening 65 leads from the piston chamber 44 tothe main body of liquid.

The lower end of each of the lower contact members 29 extends into oneof the arc extinguishing devices..|5 which is shown particularly inFigs. 2 and 7. The particular form of this arc extinguishing device isnot an important feature of our invention, but we prefer to use astructure similar to' that shown in Patent No.

l,911,072,"which was issued on an application of L. W. Dyer, et al., onMay 23, 1933, and which is assigned to the assignee of this invention.This type of arc extinguishing device comprises essentially a pluralityof superposed plates of insulating material having aligned slotstherein, these slots being adapted to form a groove or passage 61 whichis entirely lined with insulating material and within which the arc isdrawn, and being provided with cut-out portions 69 along the sidesthereof. The cut-out portions 69 form pockets for retaining the arcextinguishing fluid along the sides of the passage 61 wherein the arc isdrawn. The various plates are held together by four through bolts whichextend through insulating tubes 12. In addition to the insulating plateswhich define the walls of the arc passage, each of the arc extinguishersI5 is provided with a plurality of spaced, slotted plates 1| of magneticmaterial, which cause the arc to move transversely within the groove orare passage 61 during the arc extinguishing operation by virtue of themagnetic effect exerted thereon. This transverse movement brings the arcinto contact with the arc extinguishing fluid retained in the pockets 69disposed along the arc passage. The fluid retained therein isvolatilized, and the resulting gas is caused to flow transverselythrough the arc in venting, thereby preventing the are from restrikingafter the first current zero in the current wave. Cut-out portions insome of the insulating plates define the vent openings 13 which arespaced longitudinally along the arc passage.

An arc horn of suitable arc-resisting material is afiixed to the flange3| of the pressure chamber closure 22 in order to aid in the transversemovement of the are by the arc extinguishing device.

The bridging'memb'er I1 is provided with a pair of upstanding rodmembers 19, each of which is adapted to engage the lower end of one ofthe contact members 29. It is thus apparent that each of the contactstructures is provided witha pair of separable contact surfaceselectrically connected in series. The actuating mechanism, during thecircuit opening operation, moves the bridging member l1 and with it theupstanding contact portions 19 in the direction of the bottom of thebreaker closure. The downward movement of each of the upper contactmembers 21 is retarded by means of the dashpot action resulting from theclose engagement of the enlarged portions 31 of those members and thecooperating portions 39 of the guide members 33 therefor. As a result,the springs 6| biasing each of the lower movable contact members 29 awayfrom the upper contact members 21 cause the lower pair of separablecontact surfaces for each contact structure to remain in engagementunfit til the support members" for the biasing springs 8| engage or areengaged by the cooperating movable piston 93.

As a result, an arc is established between the cooperating contactsurfaces of each of the upper pairs of separable contact members, whichmembers separate within the upper portion of the pressure chambers 93.The heated are products resulting from this separation cause a pressureto be developed which acts on the lower end of the movable piston 99 foreach contact structure and causes that piston to move upwardly withinthe guide cylinder 99 therefor. This upward movement takes place at avery high speed, particularly when the breaker is interrupting a largemagnitude overload, and it produces two effects. First, the uppercontact surface of the lower pair of separable contacts is caused tomove away from the contact surface of the cooperating up: standingportion of the bridging member I! at a very high speed, thus eifecting avery rapid separation of each of the lower pairs of cooperating contactsurfaces. At the same time, the upward movement of the lower contactmembers 29 causes a re-engagement of each of the upper pairs ofseparable contact surfaces, thereby extinguishing the arcs which wereformed therebetween. By extinguishing the arcs which were establishedwithin the pressure chambers 93 the developing of excessive pressureswithin those chambers is prevented and the safety and reliability of theoperation of the interrupter is considerably improved. As a furtherprotection from the building up of excessive pressures within thepressure and piston chambers, the vent openings are adapted to beuncovered if the pistons 63 are moved to the extreme upward portion oftheir stroke.

When either 'of the lower contact members 29 has been moved upwardly asa result of the generationof pressure within the associated pressurechamber 49, it returns to the normal open circuit position ratherslowly, due to the fact that the only outlet for the fluid within thepiston and pressure chambers is the small vent opening 5| in the upperflange 23 and the normal leakage around the guide opening 59 for thecontact. Immediately following the separation of one of the lower pairsof separable contact surfaces and the upward movement of the lowercontact memher-29, the upper end of the are established therebetweenwill transfer to the arcing horn 15, thereby preventing undue burning ofthe lower con tact surface of the lower movable contact member 29. Theautomatic reclosing of each of the upper pairs of separable contactsurfaces likewise limits the burning of those surfaces. If desired, eachof those surfaces may be formed from a portion .9I of arc resistancematerial welded or otherwise rigidly afllxed thereto. One particularlysuitable form of material for, this use comprises a mixture of silverand tungsten in the proportions of 40% of the former and 60% of thelatter.

The rapid separation of each of the lower pairs of separable contactsurfaces which are disposed within the arc extinguishing devices effectsa rapid increase in the arc voltage of the resulting are. As a, resultlarge amounts of gas areevolved from the arc extinguishing fluidwhich iscontained within the circuit breaker enclosure and a rapid interruptionof the controlled circuit is assured.

In order to maximize the speed of separation of the lower pair ofseparable contact members,

it is desirable that the inertia of the movable as rapid a separation ofthe cooperating contact surfaces as is necessary for extremelyhigh-speed circuit interruption resulted mainly from the fact that theentire bridging structure had to be moved by the actuating mechanismduring each circuit interrupting operation. Our device, however, makespossible a. very rapid arc drawing movement which is independent of thespeed of movement of the heavy bridging members, and it is chieflythrough this means that much of the improved operation of our deviceresults.

The modified contact structure shown particularly in Figs. 5 and 6diflers in structural details from the arrangement shown in the otherfigures of the drawings. This modified structure is believed byapplicants to be somewhat less expensive to manufacture and to be morereadily applicable to existing breakers than the previously describedembodiment. It includes a tubular outer casing 9| of metal which definesthe outer walls of the pressure chamber proper 93 and which is similar,to the casing 22 of the previously described modification. This casing93 is provided with a lower flange 95 for supporting the cooperating arcextinguishing structure l5 and an upper flange 91 which is adapted toengage a suitable collar or support member 99 affixed to the lower endof the conductor illl positioned with the cooperating insulating bush- Afixed contact member I03 is rigidly supported on the support member 99,and the lower end of this contact member defines the upper contactsurface for the upper pair of, separable contact surfaces. Thewalls I95of the piston chamber 101 are cast integral with the walls 9i of thepressure chamber 99 and are machined to accommodate the movable pistonI99 which is positioned therein. The upper end of the piston chamber I0!is closed by a threaded closure member III which is provided with asuitable guide opening H9 fordetermining the path of movement of theupper movable contact member H5. A vent opening ill of smallcross-sectional area connects the pressure chamber 93 with the body ofliquid 20 contained within the main circuit breaker closure I and asomewhat larger vent H9 serves to connect the piston chamber with thatbody of liquid.

The upper movable contact member I15 is supported upon a circular platel2l through the agency of a nut I22, and is electrically connectedtosthe-lower movable contact member l23.by means of a flexible shuntI25. The plate member i 2| isbiased downwardly by a spring 121 to theupper end of the lower movable contact member I23. These rods I3 I alsopass through openings I35 in the piston I09, which is slidably movableupon the upper portion of the lower movable contact I23, and areprovided at their lower ends with enlarged portions I3I. The enlargedportions I31 cooperate with outwardly projecting fingers.I39 formedintegral with the lower contact member I23 in order to define the amountof relative movement between the upper and lower plate members I2I andI33. v

The upper end of each of the guide rods I3I terminates in a pistonportion I which moves within a dashpot I43 affixed to the top of theupper plate I2I. Suitable springs I45 are provided within these dashpotsI43 for biasing the pistons I4I toward the upper end of the dashpotchambers. A spring I 48 of considerable strength biases the two platesI2I and I23 away from each other.

The operation of this modified form of our invention is essentiallysimilar to the operation of the previously described embodiment. Uponthe occurrence of certain predetermined conditions, the actuatingmechanism begins to move the bridging member I'I downwardly toward theopen circuit position. The lower plate member I33 and with it the lowermovable contact I 23 are moved downwardly a short distance by the springI48 until the outwardly projecting fingers I39 engage the enlargedportions I31 on the ends of the guide rods I3I. When this occurs; thetwo movable contact members H5 and. I23 move as a unit under theinfluence of the upper biasing spring I21 to cause separation of theupper pair of contact surfaces, the dashpot action of the pistons I 4Iand the chambers I43 preventing the lower spring I21 from moving theupper movable contact member in the direction of the fixed contact I03.

An arc is thereupon established within the upper portion of the pressurechamber 93. This are decomposes the oil or other liquid contained withinthat chamber and almost immediately forms a considerable pressuretherein. This pressure is communicated directly to the movable pistonI09 and causes that member to move upwardly at a high speed. Veryshortly after this upward movement is initiated, the upper end of thepiston I09 engages the plate member I33 affixed to the lower movablecontact member and moves that member upwardly, thereupon efiecting avery rapid separation of the lower pair of separable contact surfaces.

As a result, a long are is formed at high speed within the arc passage61 of the arc extinguishing device I5. The magnetic action of the aremoving plates II within that device moves the arc transverselytherewithin and effects intimate contact between the arc and the liquidretained in the pockets 59. The are being drawn at high speed quicklydevelops sufllcient energy to assure the generation of an adequatevolume of gas to effect ajvery rapid completion of the arc extinguishingoperation.

Simultaneously, with the high speed separation of the lower pair ofcontact surfaces, the upwardly moving piston I09 eifects a reengaging ofthe upper pair of contact surfaces. In both of the structures shown, thereengaging of the upper pair of contact surfaces is assured. by virtueof the fact that the spring biasing the lower movable contact memberdownwardly (the spring 6| or the spring I48) is stronger than 3 77,838in, the lower circular plate I33 which is aflixed the spring biasing theupper movable contact member downwardly (the spring 35 or the springI21). This action is not so important in the embodiment previouslydescribed, but in this modified structure it is imperative that thesesprings be of dissimilar size. If the spring I48 were weaker than theupper spring I21, the upward movement of the piston I09 would not effectthe reclosing of the upper pair of contact surfaces but would merelyserve to compress the spring I 48 v The vent opening II9, which isprovided ad jacent the upper end of the path of movement of the piston I09, prevents excessive pressures from being built up within the pistonand pressure chambers, and allows the fluid normally contained withinthe piston chamber to escape freely during the upward motion of thepiston.

In the foregoing we have disclosed how very rapid separation of the maincontacts of a high capacity circuit interrupter may be efiectedthroughthe utilization of an auxiliary pair of contact surfaces which areadapted to separate prior to the separation of the main arc-drawingsurfaces. In addition, we have shown certain preferred structuralarrangements, utilizing a piston'chamber and a pressure chamber whereinthe initially separating contact surfaces are disposed for effectingthis high speed contact separation, and we have shown how thisimprovedcontact structure may be applied to an arc extinguishing chamberof the side-vented type. It is, of course, within the province of ourinvention that a contact structure employing the above describedprinciples may be applied to a circuit interrupting device utilizing anarc extinguisher of the so-called expulsion type, and it is ourintention .that the language of the appended claims should beinterpreted sumciently broadly to include such devices.

While in accordance with the patent statutes we have disclosed certainspecific structures for accomplishing the objects of our invention, the

principles of effecting rapid contact separation which we have disclosedabove are believed to be applicable to a large number of differentstructural arrangements, and we believe that improved operation ofsubstantially all types of circuit interrupters would result from theapplication of those principles thereto. In view of this, it is ourdesire that the language of the accompanying claims shall be accordedthe broadest reasonable interpretation and shall be limited by only whatis expressly stated therein and by the prior art.

We claim as our invention:

1. In a circuit interrupter, contact means having two pairs of separablecontact surfaces, actuating means for said interrupter, meanswhereby oneof said pairs of contact surfaces is the circuit interrupter is in fullopen position.

2. In a circuit interrupter, contact means havmg two' pairs of separablecontact surfaces which are electrically connected in series with eachaovassa other, actuating means for said interrupter, means defining apressure chamber within which one of said pairs of contact surfaces ispositioned, means whereby the operation of said actuating means duringthe circuit opening operation causes said pair of separable contactsurfaces positioned within said pressure chamber to separate prior tothe separation of said other pair of separable contact surfaces, andmeans operable by the pressure generated within said pressure chamber bythe heated are products resulting from the separation of said first pairof separable contact surfaces therein for efiecting a high speedseparation of said other pair of contact surfaces and for effecting areengagement of said first pair of contact surfaces in order toextinguish the are which is initially formed therebetween, and saidfirst pair of contact surfaces remaining in engagement during theopening movement of the circuit interrupter,

3. In a circuit interrupter; contact means having two pairs of separablecontact surfaces; actuating means for said interrupter; means'defining apressure chamber within which one of said pairs of separable contactsurfaces is normally positioned; means within said pressure chamberwhich evolves a gas when placed in proximity to an electric are; meanswhereby the operation of said actuating means, during the circuitinterrupting operation, causes said pair of separable contact meanspositioned within said pressure chamber to separate prior to theseparation of said other pair of separable contact surfaces, theseparation of said first pair of contact means causing an arc to beestablished within said pressure chamber which are evolves gas from saidgas evolving means; and means, including a movable piston and a cylinderwhich communicates with said pressure chamber, for separating said otherpair of contact surfaces and for returning said first-mentioned pair ofcontact surfaces into engagement where they remain in order toextinguish the are which is initially established therebetween.

4. In a circuit interrupter; contact means having two pairs of separablecontact surfaces which are electrically connected in series, meansdefining a pressure chamber within which one of said pairs of separablecontact surfaces is normally positioned; means whereby the operation ofsaid actuating means, during the circuit inter-,

rupting operation, causes said pair of separable contact meanspositioned within said pressure position.

5. In a circuit interrupter; contact nfeans'having two pairs ofseparable contact surfaces which are electricallyconnected in series;means defining a pressure chamber within which one of said pairs ofcontact surfaces is positioned; means disposed within said pressurechamber which is capable of evolving a gas when placed in proximity toan electric are; means whereby the operation of said actuating means,during the circuit sure of the gas evolved from said means disposedwithin said pressure chamber as a result of the separation of said firstpair of contact surfaces,

said piston when moved separating said other pair of separable contactsurfaces and reengaging said first pair of separable contact surfaces inorder to extinguish the arc which is initially established therebetween,and said first pair of contact surfaces remaining in engagement when thecircuit interrupter is in open position.

6. In a circuit interrupter; an enclosure, a body of liquid within saidenclosure, contact means having two pairs of separable contact surfaces,said contact means being normally submerged in said body of liquid;actuating means for said interrupter; means whereby one of said pairs ofcontact surfaces separates prior to the other of said pairs of contactsurfaces during the circuit interrupting operation; and means actuatedby the gas evolved from said liquid, as a result of the separation ofsaid first pair of contact surfaces, for separating the other of saidpairs of contact surfaces at high speed independently of said actuatingmeans and for returning said firstmentioned pair of contact surfacesinto engagement with each other where they remain so as to extinguishthe are which is initially formed therebetween.

7. In a'circuit interrupter; contact means including two pairs ofserially connected, cooper- .ating contacts; a single operating membermovable to both open and close the circuit through said pairs ofcontacts; said operating member when moved causing one of said pairs ofcontacts to be opened prior to the other during each circuit openingoperation of said interrupter and to be closed prior to the said otherpair of contacts during each circuit closing operation.

8. In a circuit interrupter; contact means, including two pairs ofseparable contacts; means for electrically connecting said pairs ofcontacts in series with each other; a single operating rod movable forboth opening and closing the circuit through said pairs of separablecontacts; means whereby one of said pairs of contacts is caused toseparate prior to the other of said pairs of contacts during eachcircuit opening operation; means whereby the heated are productsresulting from the separation of said first pair of contacts are causedto effect a high speed separation of the other of said pairs of contactsurfaces; and means for causing said first mentioned pair of contacts tobe closed prior to said last mentioned pair of contacts during eachcircuit closing oper-' ation of said interrupter.

9. In a circuit interrupter; contact means including two pairs ofseparable contacts which are electrically connected in series; meansactuated by movement of one of said contacts for both opening andclosing the circuit through said pairs of separable contacts; meanswhereby one of said pairs of contacts is caused to separate prior to theother of said pairs of contacts during each circuit opening operation;means defining the walls, of a pressure chamber within which said firstmentioned pair of contacts is positioned and is adapted to separate;means disposed within said pressure chamber which evolves a gas'whenexposed to an electric are; means whereby the gas which is evolvedwithin said pressure chamber, as a result of the separation of saidfirst mentioned pair of contacts therein, causes high speed separationof the other of said'pairs of contacts; and means for causing said firstmentioned pair of contacts to be closed prior to said lastmentioned-pair of contacts during each circuit closing operation of saidinterrupter.

10. In a circuit interrupter; contact means including two pairs ofseparable contacts which are electrically connected in series; a commonactuating member for both opening and closing the circuit through saidpairs of separable contacts; means whereby one of said pairs of contactsis caused to separate prior to the other of said pairs of contactsduring each circuit opening operation; means defining the walls of apressure chamber within which said first mentioned pair of contacts ispositioned and is adapted to separate; means disposed within saidpressure chamber which evolves a gas when exposed to an electric arc; acylinder; a piston movable therein; means whereby the pressure of thegas evolved from said means disposed within said pressure chamber as aresult of the separation of said first mentioned pair of contacts is.impressed upon said piston, said piston being movable under theinfluence of this pressure to effect the separation of said other pairof contacts, independently of said operating mechanism; and means forcaussition, in order to complete the electrical circuit therebetween;said intermediate contact means being movable during the initial stagesof each circuit opening operation of said interrupter to establish anarc between itself and said first contact means, and to subsequentlyestablish a second arc between itself and said movable contact means;means whereby the are products resulting from the initially establishedarc are caused to effect high speed separation of said movable contactmeans and said intermediate contact means, in order to increase thespeed at which said second arc is drawn; and means whereby saidintermediate contact means is caused to engage said first contact meansprior to the engagement of said movable contact means with saidintermediate contact means during each circuit closing operation of saidcircuit interrupter.

12. In a circuit breaker, contact means including at least two pairs ofserially connected cooperating contacts, a common actuating member forboth opening and closing the circuit through said pairs of contacts,means responsive during the opening movement of one of said pairs ofcontacts for delaying the separation of the other of said pairs ofcontacts, and means responsive to the separation of the first-named pairof contacts for accelerating the separation of the second-named pair ofcontacts, said last-named means causing the reengagement of saidflrstnamed pair of contacts for extinguishing the arc therebetween, andsaid first-named pair of contacts remaining in engagement when thecircuit breaker is in open position.

13. In a circuit breaker, a plurality of pairs of contacts arranged inseries, a common actuating adapted to contain an insulating fluid, meansresponsive during the initial opening movement of said actuating meansfor delaying the separation of the other of said pairs of contacts, andmeans responsive to the pressure of the insulating fluid within saidchamber created by the are upon the separation of the first-named pairof contacts for accelerating the separation of the second-named pair ofcontacts and for causing said first-named pair of contacts to bereengaged until the breaker is opened again to extinguish the arctherebetween.

14. In a circuit breaker, a plurality of pairs of contacts arranged inseries, a common actuating means for said pairs of contacts, a pressurechamber surrounding one of said pairs of contacts adapted to contain aninsulating fluid, means responsive during the initial opening movementof said actuating means for delaying the separation of the other of saidpairs of contacts, means responsive to the pressure of the insulatingfluid within said chamber created by the are upon the separation of thefirst-named pair of contacts for accelerating the separation of thesecond-named pair of contacts and for causing the reengagement of saidfirst-named pair of contacts to extinguish the arc therebetween, andmeans for maintaining the engagement of said first-named pair ofcontacts following the subsidence of pressure within said chamber.

15. In a circuit breaker, contact means comprising a pair of relativelymovable contacts and a movable conducting member interposed between saidcontacts, actuating means for opening said contacts, said conductingmember being biased toward one of said contacts for movement therewithduring the initial opening movement of said actuating means forestablishing an initial arc between said conducting member and the otherof said contacts prior to the establishing of an are between saidconducting member and said first-named contact, and means responsive tothe pressure created by the initial arc for reversing the initialmovement of said conducting member to accelerate lengthening of thesubsequently established arc.

16. In a circuit breaker, contact means comprising a pair of relativelymovable contacts and a movable conducting member interposed between saidcontacts, actuating means for opening said contacts, said conductingmember being biased toward one of said contacts for movementtherewith'during the initial opening movement of said actuating meansfor establishing an initial are between said conducting member and theother of said contacts prior to the establishing of an are between saidconducting member and said first-named contact, and means responsive tothe pressure created by the initial arc for reversing the initialmovement of said conducting member to accelerate lengthening of thesubsequently established arc and to cause the reengagement of said othercontact and said conducting member to thereby extinguish said initialarc, and follow-upmeans for maintaining said other contact and saidconducting member in engagement after 75 the subsidence of pressurecreated by said initial are.

17. In a circuit interrupter, an actuating member thereior movable toopen and close the circuit, a pair of circuit interrupting contacts, oneof which is connected to and directly moved by said actuating member, apair of pressure forming contacts connected in series with said pair ofcircuit interrupting contacts, means operable when said actuating memberis initially moved in circuit opening direction to hold said pair 01circuit interrupting contacts in engagement until aiter said 'pair ofpressure iorming contacts have separated. i5 18. In a circuitinterrupter, an actuating'member therefor movable to open and close thecircuit, a pair oi circuit interrupting contacts, one of which isconnected to and directly moved by said actuating member, a pair ofpressure forming 2 contacts connected in series with said pair ofcircuit interrupting contacts, means operable when said actuating memberis initially moved in circuit opening direction to hold said pair oicircuit interrupting contacts in engagement until after said pair ofpressure forming contacts have separated, and means for returning saidpair 0! pressure forming contacts to be in engagement when the circuitinterrupter is in open circuit position.

30 19. In a circuit interrupter, an actuating memher therefor movable toopen and close the circuit, a pair of circuit interrupting contacts, oneof which is connected to and directly moved by said actuating member, apair of pressure forming contacts connected in series with said pair ofcircuit interrupting contacts, means operable when said actuating memberis initially moved in circuit opening direction to separate said pair ofpressure forming contacts and apply the pressure formed by the arc drawntherebetween to accelerate the separation of said pair ofcircuitinterrupting contacts.

v 20. In a circuit interrupter, an actuating member therefor movable toopen and close the circuit, a pair of circuit interrupting contacts, oneof which is connected to and directly moved by said actuating member, apair of pressure forming contacts connected in series with said pair ofcircuit interrupting contacts, means operable when said actuating memberis initially moved in circuit opening direction to separate said pair ofpressure forming contacts and apply the pressure formed by the are drawntherebetween to accelerate the separation of said pair of circuitinterrupting contacts, and said means reclosing said pair of pressureforming contacts while said pair of circuit interrupting contactsmaintain the circuit interrupter in full open position.

HARRY J. LINGAL. WINTHROP M. LEEDS.

